Nasal cavity
The ethmoidal sinuses (or ethmoidal air cells) are one of the four paranasal sinuses. They are located within the ethmoid bone. They are present at birth and they develop rapidly from 0-to-4 year-old; they further mature from 8-to-12 year-old during puberty. They lie between the orbit and the nose within the ethmoid labyrinth. Bony septa separate the sinus into multiple air cells (3-18). The lateral wall of the labyrinth, in the medial part of the orbit is called the lamina papyracea. 'The roof of the labyrinth is covered by the the orbital part of the frontal bone. The medial wall articulate with the cribiform plate of the ethmoid. Cells are divided into anterior, middle and posterior cells based on the location of drainage. *'Anterior ethmoid air cells: occupy the anterior part of the sinus. Roofed by the frontal bone. The ostia open into the infundibulum in the middle meatus or frontonasal duct. *'Middle ethmoid air cells: '''drain into the middle meatus. One or more project as a convexity into lateral wall of the nose under cover of the middle concha forming the ethmoidal bulla. *'Posterior ethmoid air cells:''' ostia opens into the superior meatus. The most posterior cells extend far enough back to lie immediately adjacent to the optic nerve in its canal. Some of the ethmoidal air cells have their own name, because of their importance in surgical procedures or their involvement in head and neck pathologies: * Haller cells are also known as infraorbital ethmoidal air cells. They are extramural ethmoidal air cells that extend into the inferomedial orbital floor and are present in ~20% (range 2-45%) of patients, depending on their exact definition. In most instances they are asymptomatic and they are generally not thought to be associated with increased rates of sinusitis. They may become clinically significant in a number of situations: ** become infected, with the potential for extension into the orbit ** may narrow the ipsilateral ostiomeatal complex (OMC) if large and may thereby predisposing the ipsilateral maxillary antrum to obstruction ** may lead to inadvertent entry into the orbit if unrecognised at endoscopic surgery * Agger nasi air cells are the most anterior ethmoidal air cells lying anterolateral and inferior to the frontoethmoidal recess and anterior and above the attachment of the middle turbinate. They are located within the lacrimal bone and therefore have as lateral relations the orbit, the lacrimal sac and the nasolacrimal duct. They are identified in 90% of patients, and should not be confused with Haller cells(located along the medial floor of the orbit) or supraorbital air cells (located in the orbital roof). The may contribute to chronic frontal sinusitis . * Sphenoethmoidal (or Onodi) air cell is defined as an ethmoidal air cell that lies posteriorly to the sphenoid sinus. Rarely it may lay superiorly to the sphenoid sinus and is called a central Onodi air cell. As a result of its location the optic nerve, and less commonly, the internal carotid artery, are very closely related with as little as 0.03 mm (median 0.08 mm) of bone separating them. The incidence is variable with sphenoethmoidal air cells present in up to 60% of cadavers in one series, although the figures usually quoted in Western populations is ~10% (range 8-13%). Potential damage to the optic nerve and ICA occurs when attempts to enter the sphenoid sinus endoscopically are made by passing through what is thought to be the posterior most ethmoidal air cell, while it is instead an sphenoethmoidal cell. Other pathology such as isolated mucocoeles, squamous cell carcinoma and sinusitis have all been reported in sphenoethmoidal air cells, leading to early optic nerve involvement. Blood supply: branches from the supraorbital, anterior and posterior ethmoidal and sphenopalatine arteries. Lymph drainage: submandibular and retropharyngeal node Nerve supply: supraorbital, anterior and posterior ethmoidal, lateral posterior superior nasal nerves. Hence both ophthalmic and maxillary branches of the trigeminal supply the ethmoidal sinus.